The present invention relates to the injection of pharmaceuticals and other medical liquids. It finds particular application in conjunction with human and veterinary injections. More specifically, it relates to an improvement in which the medical liquid is placed in a flexible envelope and injected under pressure.
Recent medical developments have resulted in new processes for analyzing and controlling the state of patients. Among these processes are analyses which are performed after injection of a contrast agent. Contrast agents may be used, for example, an angiographic analyses. In angiography, an iodine solution is injected into the vessels, veins, and arteries, in order to render them opaque to radiation and to impregnate tissues and organs with the opacifying substance. The contrast agent helps to emphasize and determine the presence of possible thromboses, embolisms, compressions, and other abnormalities in radiographic images.
Contrast products are also used in scanning procedures or during traditional or digital angiography. The contrast agent is injected into the vein or artery at rates ranging generally from 0.5 to 35 ml/sec. to form a bolus of the contrast agent moving through the veins or arteries. There are, however, alternate types of injections other than injections of contrast agents, such as transfusions, procedures for artificial nutrition by blood or by digestive route (enteral or parenteral).
Prior injection devices include syringes including the liquid to be injected. The syringe has an injection head which is connected to a hypodermic or intravenous needle or to a catheter by interconnecting flexible tubing. Often, the tubing includes an anti-retention threshold valve. Conventional syringes are prepared by filling and air removal from flasks of different contents, such as 60, 100, 200 ml, or even 500 ml. In view of the increasing requirements in areas of hygiene and with respect to patients, it is desirable to deliver a non-contaminated product to several patients. It is desirable to avoid, to the greatest degree possible, any decantation from flask to syringe, particularly if the syringes are destined to serve several patients. This avoids any risk of retrograde contamination by drawing fluids from a patient back into the syringe. The development of contagious diseases, specifically the development of the AIDS disease, has motivated physicians to increase requirements in the area of hygiene. It is thus a determining factor and extremely important to suppress all risks of contamination and avoid, to the maximum extent possible, decantations of initially required products and to do so primarily for purposes of hygiene and safety. Thus, devices have been conceived in which the medical liquid is stored in packaging which includes a flexible pouch fitting with a coupling. The pouch replaces the traditional syringe. The pouch coupling is connected to tubing which is linked to an injection conduit, such as a catheter or hypodermic needle, intravenous or other. The flexible pouch is placed in a casing that includes an inert motive liquid which is placed under pressure.
Such devices are described, for example, in European Patent Application Nos. 0 343 286 and 0 676 214, in U.S. Pat. No. 3,199,511, as well as in French Patent Application No. 2,592,306. In all of these devices, a flexible pouch contains the liquid to be injected. The pouch is placed in an enclosure containing the motive liquid which is placed under pressure to propel the liquid contents from the pouch. These devices, however, present drawbacks in their modes of utilization and construction. In fact, certain devices are not very practical for users, specifically when changing the flexible pouch or ridding the pouch bubbles. Additionally, in some instruments, the pressure distribution over the pouch is unsatisfactory, decreasing accuracy of regulation of the injection parameters. This is due in part to the flexible pouch gradually changing in flexibility or shape with use. Furthermore, all of these devices are intended only to performing perfusions and in no case are they held out as suitable for the injection of contrast agents.
The present invention proposes a simple, new device which overcomes the above-referenced problems, yet is easy to use, reliable, and accurate.